Prenatal Expanded Carrier Screening Tests Can Be Difficult To Interpret : Shots - Health NewsA variety of genetic tests are available to screen both fetus and parents. One option that's growing in popularity is called an expanded carrier screening. The results can be useful and overwhelming.

Shara and Robert Watkins hold their 5-month-old daughter, Kaiya, in their home in San Mateo, Calif., just after she had woken up from an afternoon nap.
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Shara and Robert Watkins hold their 5-month-old daughter, Kaiya, in their home in San Mateo, Calif., just after she had woken up from an afternoon nap.

Lindsey Moore/KQED

It wasn't hard for Shara Watkins to get pregnant. It was hard for her to stay pregnant.

In 2016, she was devastated by two miscarriages. With the help of several medications, she successfully carried a child last year.

Shara and her husband, Robert, were elated when she reached her second trimester, the phase when the highest risk of miscarriage subsides.

Unfortunately the San Mateo, Calif., couple's struggles continued.

Shara spent four months of her pregnancy on bedrest. When their doctor offered extensive genetic testing to check the health of their fetus, the couple leaped at the opportunity. Shara had a history of rare disease in her family.

"I had a high-risk pregnancy, and there had been a lot of complications prior to this," says Shara. "And, so I just wanted to have all the information that I could."

Glut of information available to expecting parents

In the past, doctors may have screened parents for a few suspect diseases common to their specific ethnicity or family history. But now a growing number of companies offer extensive panels testing for hundreds of rare diseases.

"Over the last 10 to 20 years the number of genetic disorders that we are able to test for has exploded," says Dr. Mary Norton, a prenatal geneticist at University of California, San Francisco.

Silicon Valley is a hotbed for companies vying for the business of concerned future parents. The prenatal genetic testing industry is projected to grow nearly 30 percent over the next five years.

A wide variety of tests are now available to screen both fetus and parents. One option that's rapidly growing in popularity is called an expanded carrier screening.

About a dozen lab companies, most based in the San Francisco Bay Area, can scan a patient's blood or saliva for hundreds of conditions that their child could inherit.

A perfectly healthy parent can pass along an autosomal recessive disease like cystic fibrosis or Tay-Sachs, if their partner is also a carrier for the disease. When both parents have a mutated version of the same gene, then their child is at an increased risk for developing a condition.

"In these types of diseases, 80 percent of the time there's no family history," says Jim Goldberg, chief medical officer of Myriad Women's Health. Norton agrees that family history is not a very sensitive screening tool.

The ideal time to take a carrier screening is prior to conception because in vitro fertilization is still a possibility.

If both parents are found to be carriers of the same disease, IVF allows doctors to ensure a healthy fertilized egg by genetically screening the embryos before conception.

The tests must be prescribed by a doctor and screening panels vary widely in price. For example, a call to the customer service line for Myriad Genetics' lab in South San Francisco led to a price quote of $1,599 for patients who don't have insurance.

Gifty Hammond prepares DNA samples at Myriad Genetics lab in South San Francisco.

Lesley McClurg/KQED

But if you pay within 45 days, the price drops to $349. Shara and Robert paid about $600 out of pocket for their two screening panels from a Bay Area company called Natera. The company charged their insurance about $3,200 for both tests.

Does knowing more help?

When Shara and Rob's doctor emailed their tests results, the couple was alarmed because their physician suggested they see a genetic counselor to help them interpret the report.

"This new landscape is complicated and it's beyond the ability for most OB-GYN's to really understand it themselves and explain it well," says UCSF's Norton.

It appeared the Watkin's baby could inherit spinal muscular atrophy, or SMA, a potentially fatal disease. The couple hadn't discussed what they would do if their child was unhealthy.

"I called Rob in pure hysterics on my way to work," says Shara.

"When I got the call in my office she was crying," recalls Rob. "We were both in kind of a panic mode immediately."

Rob and Shara spent the day poring over page after page of testing results, and then subsequent days searching the Internet for answers.

"The test results give you kind of these alerts on the first page like you're a carrier for this, your carrier for this," Shara says. "It's definitely not clear. I mean, if it had been clear we wouldn't have ever gone into full panic mode."

Find an expert

Although Shara and Rob could have sought free counseling from one of Natera's genetic counselors, they chose an unaffiliated expert. They booked the first available appointment at Stanford Children's Health. Stanford billed $642 to Shara's insurance for the consultation. Her plan paid $352.

"They came to us with this information not knowing what it meant, not knowing what the risks were and not understanding the implications," says Meg Homeyer, a genetic counselor at Stanford. "Plus, the language is difficult to interpret and sometimes can sound alarmist."

As it turns out, Shara, Rob and their doctor thought their baby's risk of SMA was a lot higher than it was. The report says they were at an increased carrier risk, but that isn't the same thing as being an actual carrier for the disease.

"It was much more lower, more like 3,500," says Homeyer as she thumbed through the test results. Yet, even though Rob and Shara's worst fears didn't play out, they still lost sleep at night wondering if their child could be the 1 in 3,500.

Making sense of risks

Homeyer says she frequently sees parents agonize over how to feel, or whether to act on abstract numbers.

"They will not know whether a baby is 100 percent healthy until birth," says Homeyer. "In the meantime they're trying not to worry about the risks but they can't help it."

Homeyer says the value of a test is dependent on the values of an individual couple.

"There's the family that will want every possible test available," says Homeyer. "They'll want no stone unturned because their tolerance for risk is low. There are other families where this information in pregnancy isn't useful for them."

Like families who would not seek further diagnostic testing, or potentially terminate a pregnancy regardless of testing results.

"We often have people who say, 'I wish I had never started down this path,' " says Norton. "Although I don't think people can really anticipate how they'll feel until they get there."

One test leads to the next

For those who choose to do a carrier screening, the worst-case scenario is their child has a 1 in 4 chance of inheriting an autosomal recessive condition. Further diagnostic invasive testing like an amniocentesis is necessary to confirm the possibility. Fortunately, care for rare diseases has improved dramatically in recent years.

"Many more of these conditions are treatable after birth," says Norton. "And treatment starting right at the time of birth may improve the outcomes. In some cases we can even start treatment during pregnancy."

Norton says the advent of more advanced testing stirred a lot of fear among practitioners that abortion rates would simultaneously rise, but that's not what preliminary studies are showing.

Why scanning for more diseases isn't always better

If you're the type of parent who does want as much information as possible, you may be inclined to take the most comprehensive test on the market. However, Aleks Rajkovic, chief genomics officer at UCSF, cautions families attracted to extensive panels.

"A lot of them are overkill," says Rajkovic. "Some panels are testing for very rare disorders that have only been seen in a single family, so the likelihood of a client ever actually having the variation is infinitely small."

Plus, he says extremely rare disease are usually not well studied or understood, so it's very hard for doctors to offer helpful information about what a prognosis could entail.

Fortunately Shara's little girl, Kaiya, is a healthy 5-month-old. When asked if Shara would go back and take the genetic test again, she pauses, but then nods yes.

Even though she spent months fretting over the tiny possibility her child wasn't ok, she says the anxiety she dealt with was better than not knowing anything all. Her advice to future parents is think carefully about whether more information will, for them, be reassuring or just another thing to worry about.

Norton agrees. She hopes families focus on a key fact: 97 percent of babies are born perfectly healthy.

Correction April 8, 2019

A previous Web version of this story incorrectly listed Fragile X syndrome as an example of an autosomal recessive disease. In fact, Fragile X syndrome follows an X-linked dominant pattern of inheritance.